title: Structural basis for a homodimeric ATPase subunit of an ECF transporter.
abstract: The transition metal cobalt, an essential cofactor for many enzymes in prokaryotes, is taken up by several specific transport systems. The CbiMNQO protein complex belongs to type-1 energy-coupling factor (ECF) transporters and is a widespread group of microbial cobalt transporters. CbiO is the ATPase subunit (A-component) of the cobalt transporting system in the gram-negative thermophilic bacterium Thermoanaerobacter tengcongensis. Here we report the crystal structure of a nucleotide-free CbiO at a resolution of 2.3 Å. CbiO contains an N-terminal canonical nucleotide-binding domain (NBD) and C-terminal helical domain. Structural and biochemical data show that CbiO forms a homodimer mediated by the NBD and the C-terminal domain. Interactions mainly via conserved hydrophobic amino acids between the two C-terminal domains result in formation of a four-helix bundle. Structural comparison with other ECF transporters suggests that non-conserved residues outside the T-component binding groove in the A component likely act as a specificity determinant for T components. Together, our data provide information on understanding of the structural organization and interaction of the CbiMNQO system.
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing, 100083, China.
authors.forename: Chengliang
authors.initials: C
authors.lastname: Chai
authors.forename: You
authors.initials: Y
authors.lastname: Yu
authors.forename: Wei
authors.initials: W
authors.lastname: Zhuo
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zhao
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Li
authors.forename: Na
authors.initials: N
authors.lastname: Wang
authors.forename: Jijie
authors.initials: J
authors.lastname: Chai
authors.forename: Maojun
authors.initials: M
authors.lastname: Yang
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry; D001692:Biological Transport; D020134:Catalytic Domain; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D046968:Thermoanaerobacter / Q000201:enzymology
chemical_list: D000596:Amino Acids; D003035:Cobalt; D000251:Adenosine Triphosphatases